The overall goal of this research is to explore the range of immunoglobulin (Ig) diversity within and between species. The work is divided into two main projects. 1. Diversity of Lambda chains in mouse immunoglobulins. The variable (V) as well as the constant (C) regions of the lambda chains in inbred mice are encoded by a very limited number of germ-line genes. To obtain insight into the extent of somatic diversification of these genes, we are determining the amino acid sequence of a number of Lambda V regions. We also wish to establish correlations between limited changes in sequence and the three-dimensional structure and function of Lambda-containing antibodies. In contrast to inbred strains, randomly-bred wild mice appear to have a greatly expanded number of genes for Lambda C regions. It is not known, however, how many of these genes are actually used in Ig synthesis. We will investigate the expression of Lambda genes in wild mice by studying Lambda chain production and gene rearrangements in hybridomas obtained by fusing spleen cells from wold mice with myeloma cells from BALB/c mice. 2. The immune system in developing amphibians. The first major group of vertebrates to possess more than one Ig class are the anuran amphibians. Since these animals have a free-living larval form, they are excellent subjects for investigations of the development of the immune system from both a phylogenetic and ontogenetic perspective. To evaluate changes in Ig synthesis during development and to determine similarities and differences from mammalian immune responses, we have been characterizing the Igs in adult and larval Rana catesbeiana. In addition, we plan to utilize recombinant DNA technology to investigate the structure and organization of Ig genes in Xenopus laevis. The proposed studies may provide insight into the evolution of mechanisms for generating antibody diversity.